Reports of a patient in Canada who was hospitalized with “Ebola-like symptoms” after returning from West Africa were premature, World Health Organization (WHO) officials said Tuesday.

But in Guinea, Ebola already has killed nearly 60 people. Across the border in Liberia, officials are investigating five deaths suspected of having links to the Guinea outbreak of the disease, which causes severe bleeding and can have a 90 percent fatality rate.

Health officials in Saskatchewan, Canada, said a critically ill patient in Saskatoon had recently returned from Liberia. The patient has been isolated, and nursing staff are using gloves, masks and other protections to avoid infection through contact with bodily fluids, the officials said.

At a news conference in Geneva, WHO officials discussing the outbreak of the disease in Guinea, said preliminary tests on the patient in Canada had been negative for Ebola.

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Ebola can cause sudden fever and intense weakness, followed by vomiting, diarrhea and internal and external hemorrhaging. Although Ebola is terrifying, there have been little more than 20 outbreaks of it or related viruses since it was discovered in 1976, and all have been contained rapidly by isolating victims and those who have been in contact with them.

Almost 40 years after Ebola emerged from the jungles of Africa as one of the world’s most lethal diseases, scientists are beginning to close in on treatments that may be able to stop the virus.

The relative rarity of Ebola outbreaks, largely limited to rural areas of poor African nations, makes the disease an unattractive target for big drugmakers. Instead, much of the research to fight Ebola has been funded by the U.S. government. Tekmira Pharmaceuticals, for example, began its first human trial of a drug in January with backing from the Defense Department.

Ebola is among a group of diseases that are so deadly and easy to spread that they pose a risk to national security, according to the U.S. Centers for Disease Control and Prevention. The agency lists the virus as a Category A bioterrorism agent, alongside anthrax and smallpox.

Tekmira’s product, known as TKM-Ebola, is being developed under a $140 million contract with the Defense Department’s Medical Countermeasure Systems BioDefense Therapeutics Joint Product Management Office. Tekmira, based in Burnaby, Canada, this month won fast-track designation from the U.S. Food and Drug Administration to develop the experimental treatment.

“It’s a really exciting time to be working on Ebola right now,” said Erica Ollmann Saphire, a professor at the Scripps Research Institute in La Jolla, Calif., who’s leading a consortium of 15 public and private institutions to develop treatments to fight the virus. “There are already candidate cocktails that can be used in an emergency.”

The U.S. National Institutes of Health (NIH) last week gave a five-year grant of as much as $28 million to Saphire’s group, which is collaborating on antibody cocktails to fight Ebola. Saphire said she didn’t know if any of the experimental treatments were being used in the Guinea outbreak.

While HIV, the AIDS-causing virus that also jumped from animals to humans in Africa, has spawned dozens of approved drugs and a $14 billion market, the small number of Ebola cases is a deterrent for big drug companies, said Stephan Guenther, head of the Bernhard Nocht Institute for Tropical Medicine in Hamburg, Germany.

“If you count all the cases of Ebola since the discovery, it’s below 10,000, so it’s definitely not of commercial interest,” he said.

Guenther led a team of researchers that showed an experimental treatment called favipiravir, developed by a unit of Japan’s Fujifilm as a treatment against influenza, cleared Ebola virus and prevented mice from dying in a study published in February.

He said the most promising drug in development is a cocktail of antibodies developed by Mapp Biopharmaceutical in San Diego with the Defense Advanced Research Projects Agency, the NIH and the Defense Threat Reduction Agency.

In research with monkeys, the cocktail prevented 43 percent of those with symptoms of Ebola from dying in a study published in Science Translational Medicine.

Two cancer drugs from Novartis — Gleevec and Tasigna — fought the Ebola virus, according to a study published in 2012.

GlaxoSmithKline last year paid $345 million for Okairos, a Swiss vaccine developer with early-stage products against diseases including Ebola. Inovio Pharmaceuticals, a Blue Bell, Penn.-based company, said last year its experimental vaccine against Ebola protected guinea pigs against the virus.

The virus, first identified in the 1970s near the Ebola River in what is now the Democratic Republic of the Congo, is transmitted to people through the blood and other secretions of wild animals such as chimpanzees, gorillas, bats and porcupines, according to the WHO. Humans transmit the virus to each other through contact with blood and other body fluids.

The deadliest recorded outbreak was in the Democratic Republic of the Congo in 1995, when 254 of the 315 people infected died, according to the WHO. All the outbreaks in the past decade have been in the Democratic Republic of the Congo, the neighboring country of Congo, and Uganda, and one outbreak in Sudan in 2004.

“Experience shows that there is a low risk for travelers. People who get Ebola tend to get very sick very fast, and they are not really able to travel. That’s why these outbreaks usually are self-contained,” said WHO spokesman Tarik Jasarevic.